The present invention relates to a control module which controls the engine of an automobile or the like and, more particularly, to an electronic device which is suitable for integral attachment to an actuator controlling the engine.
A conventional device for controlling the engine of an automobile is mounted in the passenger compartment. For this purpose, both the control circuit elements constituting the electronic device and the individual parts for removing noise from lead wires are attached by a eutectic solder with a low melting point.
In recent years, however, it has become necessary to integrally attach such an electronic device to the carburetor, etc., because it is necessary to mount the electronic device in the vicinity of an actuator. Since the various elements of the electronic device cannot stand being attached by eutectic solder, it is the current practice that the parts other than those for which the eutectic solder must be used are attached by a solder with a high melting point. More specifically, the control circuit elements, such as power transistors, ICs, and capacitors, are attached to the control circuit substrate by a high-temperature solder, and then the individual parts, such as diodes for filtering out noise from the lead wires, are attached by a eutectic solder. These attachment operations are conducted after the entire control circuit substrate is heated to 330.degree. C. for the high-temperature solder, and after the entire control circuit substrate is heated to 230.degree. C. for the eutectic solder. Since the substrate is heated again after the first attachment operation, the electronic device of the prior art has the defect that the lives of the control circuit elements are reduced.